---
id: CVE-2026-64380
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb: client: harden POSIX SID length parsing

  posix_info_sid_size() reads sid[1] to obtain the subauthority count,
  but its existing boundary check still accepts buffers…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb: client: harden POSIX SID length parsing

  posix_info_sid_size() reads sid[1] to obtain the subauthority count,
  but its existing boundary check still accepts buffers…
severity: high
cvss: 8.2
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.7, < 5.10.261'
  - 'linux_kernel >= 5.11, < 5.15.212'
  - 'linux_kernel >= 5.16, < 6.1.178'
  - 'linux_kernel >= 6.2, < 6.6.145'
  - 'linux_kernel >= 6.7, < 6.12.96'
  - 'linux_kernel >= 6.13, < 6.18.39'
  - 'linux_kernel >= 6.19, < 7.1.4'
  - linux_kernel = 7.2
patched:
  - linux_kernel 7.1.4
published: '2026-07-25'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T14:06:05.950'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64380'
references:
  - url: 'https://git.kernel.org/stable/c/0de5b8e76847f5de26f364a82c6602c4881c30da'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/171605aed68380c2fa75dff9b3a1ed427c50065b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4213c1208978483021d7d125c131de3985d38f61'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/427eb7eb46425fec845a43e861f3d6e2899cae59'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/46a84715a015cb48e1b9c219dc88c03d8a541ea4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7ad2bcf2441430bb2e918fb3ef9a90d775a6e422'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/86c5d470f5d42e61123b2f4b4f0b91f4eee5b980'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/96e889bc1e759c83f25093e8c2f3da31b4973f30'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00443
epssPercentile: 0.35895
ingestedAt: '2026-07-27T06:16:50.963Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

smb: client: harden POSIX SID length parsing

posix_info_sid_size() reads sid[1] to obtain the subauthority count,
but its existing boundary check still accepts buffers with only one
remaining byte. Require two bytes before reading sid[1] so all client
paths that reuse the helper reject truncated POSIX SIDs safely.

## Affected

- `linux_kernel >= 5.7, < 5.10.261`
- `linux_kernel >= 5.11, < 5.15.212`
- `linux_kernel >= 5.16, < 6.1.178`
- `linux_kernel >= 6.2, < 6.6.145`
- `linux_kernel >= 6.7, < 6.12.96`
- `linux_kernel >= 6.13, < 6.18.39`
- `linux_kernel >= 6.19, < 7.1.4`
- `linux_kernel = 7.2`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.1.4`